Would the Card BIOS even handle the new memory? Or would you have to find an existing card that they did that to and flash each to a new BIOS to compensate?

I doubt that the original BIOS could run with the upgrade, but this is a realm above and beyond my scope TBH.

I think upgrading the quantity of RAM may not work as it's not going to be "mapped" in.

However, if you found the same style RAM ICs, but at a faster rated speed then that would give you some nice OC room and I can't really see that not working, providing the controller was never the bottleneck in the first place.